The common combustion engine burns gaseous or liquid fluids in the compressed air. In the near past the fuel fluids, especially gasoline and keroseen, have become rare and expensive. To prevent the extinction of available fuel, great efforts and investments are planned to transform natural coal into liquid fuel or gaseous fuel. The transformation process to change natural coal into useable liquid or gaseous engine fuel requires high amounts of energy for processing. About two thirds to three fourth of the available amount of coal is commonly required for the processing, while the rest of only one fourth to one third of the utilized amount of coal becomes a gasoline, kerosene or other liquid-or gaseous-fuel.
While the liquidifaction of natural coal into liquid-fuel itself is rather economical, the processing wastes more energy than liquidified energy is obtained.
The natural amount of coal available in the resources of the earth would last two to three times longer and the costs of preparation of fuel from natural coal would be drastically less expensive, when solid blocks of coal fuel could be used in a combustion engine.